Water in maps?

Hi!
I've made a quick search over the forum and I saw no topics about this, so if I forgot something, I apologize. As I'm making a map, I want to put some water on it, but after several tries, I got no result until the moment. I press "Add water" in the Tile menu, then I go to Terrain and after setting a height for water and selecting it instead of terrain, there is no effect on the tile. What am I doing wrong, or what's the way to put it?

You have to add water, then lower the land. Then in terrain tools you select water and use rise/lower (not set height) to adjust the water level.